This patent deals with the synthesis of single graphene sheets decorated with metal or metal oxide nanoparticles, and their uses.
There is much attention given in the prior art publications with respect to graphite oxides intercalated with polymers and surfactants to keep the graphene oxide separated but nobody to date has produced single graphene sheets decorated with metal nanoparticles and their application for energy storage, generation, and conversion devices.
Fuel cells, batteries, super capacitors, and solar cells among others are key devices to meet the increasing energy needs, energy security and concerns compatible with a green environment. Hydrogen storage, for example, is a critical issue for the success of hydrogen economy.
The development of transportable and highly reversible hydrogen storage systems is important to the scale-up of hydrogen energy-based technologies, especially for on-board transportation applications.
Hydrogen, because of its low density, easy and unlimited availability, and non-polluting and renewable characteristics has emerged as a promising energy source; as a solution to the world energy crisis arising from the fast rate of depletion of fossil fuels. The implementation of an efficient, secure and viable hydrogen based system is restricted by certain scientific and technological challenges in hydrogen storage.
On-board application, which currently depends heavily on petroleum based fuels, requires a reliable, lightweight, reversible, safe, efficient and economically viable storage system for hydrogen as a fuel. To make hydrogen fuel economy technically viable and economically feasible, the U.S. Department Of Energy has defined the targets for hydrogen storage within the vehicular constraints of storage efficiency (mass % and volume %), refueling time, safety and cost.
For on-board automotive applications, the storage capacity at ambient conditions has been targeted as 6.5 weight %, (45 kg/m3) and 9 weight %, (81 kg/m3) by 2010 and 2015, respectively.
Among the possible methods of compression, liquefaction and adsorption on solids (carbon nanostructures, zeolites and metal organic frameworks), the last option has caught the attention of researchers because of its safe and relatively simple engineering design. Carbon nanostructures, especially because of their advantages of availability, high surface area, fast kinetics and complete reversibility are in the focus of the scientific community.
New engineered materials are required to accomplish high electro-catalytic activity, high power/current, high capacitance, high solar energy conversion, and high hydrogen uptake for such applications, respectively.
It has been discovered by the inventors herein that single graphene sheets decorated with metal or metal oxide nanoparticles and having high surface areas in excess of 1500 m2/g, provide opportunities for energy conversion and storage devices, for example, hydrogen storage.